Energetics

Question 1

suggest one reason why extracting vanadium is expensive other than the costs of heating the reaction mixture?

Answer 1

Calcium is produced in the reaction. This is expensive to extract because it requires an immense amount of electricity. Electrolysis.

Question 2

The equation for the reaction of Aluminium with iron 3 oxides.

Answer 2

2AL + Fe2O3 –> Al2O3 + 2Fe

Question 3

Identify two hazards with the process of making vanadium using HCL other than temp

Answer 3

HCL is corrosive and hydrogen gas is flammable.

Question 4

Deduce why this process produces pure vanadium other than the fact purified VCL2 is used.

Answer 4

The only other product produces is HCL which is a gas and it can therefore escape.

Question 5

Why does Cl4 have a bond angle of 109.5

Answer 5

This is due to it having no lone pairs and 4 bonding pairs. Therefore they repel each other equally and spread as far as possible.

Question 6

the reaction of iron with antimony sulfide to form antinomy and iron 3 sulfide

Answer 6

3Fe + Sb2S3 –> 2sb + 3Fes

Question 7

One substance that is manufactured directly from sulfur dioxide is formed in this reaction.

Answer 7

Sulfur Trioxide

Question 8

Why is the method of extraction from antinomy from a low-grade core ore is described as a low-cost process

Answer 8

Because it is a single-step process

Question 9

suggest one other source of error in the student’s experiment

Answer 9

It was incomplete combustion

Question 10

Suggest one reason why using a powdered catalyst increases the rate of reaction

Answer 10

It increases the collision frequency and the contact between the solids.

Question 11

Suggest one major reason why this method of extracting strontium is expensive

Answer 11

Aluminum extract requires a large amount of energy due to it being extracted by electricity.

Question 12

Why does calcium have a higher melting point than strontium

Answer 12

calcium has a stronger attraction between the cations and the delocalized electrons

Question 13

Write the equation for magnesium and cold water

Answer 13

Mg + 2H2O –> 2Mg (OH)2 + H2

Question 14

Give a medical use for the magnesium compound formed in the reaction of magnesium with cold water

Answer 14

Magnesium oxide is used to relieve indigestion and neutralize stomach acids

Question 15

deduce the role of the bacteria in this reaction

Answer 15

A catalyst to speed up the reaction

Question 16

Standard enthalpy of combustion

Answer 16

This is the enthalpy change when one mole a substance is burnt in excess oxygen with all the reactants and products under standard conditions

Question 17

What are standard conditions?

Answer 17

298K

100kpa

Question 18

Standard enthalpy of formation

Answer 18

This is the enthalpy change when one mole of a substance is produced from its constituent elements under standard conditions.

Question 19

Suggest two reasons why the value obtained by the student is different from the value calculated

Answer 19

• Reactants not in standard condition
• incomplete combustion
• Energy has been lost to the surroundings due to heat loss

Question 20

state a change in volume of water that would cause a reduction in heat loss

Answer 20

Increase in volume as there is increased contact between the colorimeter and the water.

Question 21

A 50g sample of water was used. Explain how you could measure out this water without using a gas syringe

Answer 21

Water has a known density of 1gcm3 and therefore a volume of 50cm3 could be measured out

Question 22

write an equation for the fermentation reaction?

Answer 22

C6H1206 —> 2CH3 CH2OH + 2CO2

Question 23

give two essential conditions for the reaction to produce a good yield of ethanol.

Answer 23

Enzymes from yeast and conditions are aerobically

Question 24

Name the process used to produce a much more concentrated solution of ethanol from a dilute aqueous solution.

Answer 24

Fractional distillation

Question 25

What is carbon neutral

Answer 25

this is that there is no net overall carbon dioxide emission to the atmosphere

Question 26

Mean bond enthalpy

Answer 26

the average energy change over a range of molecules needed in breaking covalent bonds

Question 27

deduce the steps needed to determine an accurate minimum temperature that is not influenced by heat from the surroundings

Answer 27

• Star a clock watch when the substance is added to water
• Record the temperature every min for 5 min
• Plot a graph temperature vs time
• extrapolate back to the time of mixing and determine the temperature

Question 28

Lattice enthalpy of disassociation

Answer 28

enthalpy of solution = lattice enthalpy + hydration enthalpy of both ions.

• Rearrange the equation
• make sure that you x2 if the question mentions chloride ions

Question 29

why is your answer from lattice enthalpy off disassociation for magnesium chloride

Answer 29

Mag ion is smaller than calcium ions, therefore, this attracts chloride ions more strongly due to ionic bonding.